firecrawl/open-lovable · error · Error

No available method to write files to sandbox

Error message

No available method to write files to sandbox

What it means

writeFileToSandbox throws this when the sandbox object exposes none of the supported write mechanisms: no provider-native writeFile, no alternative write API, and no sandbox.commands.run. It is a capability-detection failure — the injected sandbox is not a recognized provider that this library knows how to write files with.

Source

Thrown at lib/morph-fast-apply.ts:165

    const escaped = content
      .replace(/\\/g, '\\\\')
      .replace(/"""/g, '\"\"\"');
    await sandbox.runCode(`
import os
os.makedirs(os.path.dirname("${fullPath}"), exist_ok=True)
with open("${fullPath}", 'w') as f:
    f.write("""${escaped}""")
print("WROTE:${fullPath}")
    `);
  } else if (sandbox?.commands?.run) {
    // Shell redirection (fallback)
    // Note: beware of special chars; this is a last-resort path
    const result = await sandbox.commands.run(`bash -lc 'mkdir -p "$(dirname "${fullPath}")" && cat > "${fullPath}" << \EOF\n${content}\nEOF'`, { cwd: '/home/user/app', timeout: 60 });
    if (result?.exitCode !== 0) {
      throw new Error(`Failed to write file via shell: ${normalizedPath}`);
    }
  } else {
    throw new Error('No available method to write files to sandbox');
  }

  // Update backend cache if available
  if ((global as any).sandboxState?.fileCache) {
    (global as any).sandboxState.fileCache.files[normalizedPath] = {
      content,
      lastModified: Date.now()
    };
  }
  if ((global as any).existingFiles) {
    (global as any).existingFiles.add(normalizedPath);
  }
}

export async function applyMorphEditToFile(params: {
  sandbox: any;
  targetPath: string;
  instructions: string;

View on GitHub (pinned to 69bd93bae7)

Solutions

1. Pass a supported sandbox instance created via SandboxFactory.create ('e2b' or 'vercel') that implements commands.run or a native write method.
2. Inspect the sandbox object at runtime (log Object.keys(sandbox)) to see which methods it actually exposes.
3. Update custom providers/mocks to implement the expected provider interface (commands.run or writeFile).
4. Pin/verify sandbox SDK versions so the API surface (commands.run) matches what this library expects.
5. Catch the error early at sandbox setup time with a capability check rather than mid-edit.

Example fix

// before
await applyMorphEditToFile(anyObjectPassedAsSandbox, path, edit);
// after
if (typeof (sandbox as any)?.commands?.run !== 'function' && typeof (sandbox as any)?.writeFile !== 'function') {
  throw new Error('Sandbox instance does not support file writes (needs commands.run or writeFile)');
}
await applyMorphEditToFile(sandbox, path, edit);

function sandboxCanWrite(sandbox: any): boolean {
  return typeof sandbox?.writeFile === 'function' ||
    typeof sandbox?.commands?.run === 'function' ||
    typeof sandbox?.files?.write === 'function';
}
if (!sandboxCanWrite(sandbox)) throw new Error('Sandbox does not support file writes');

function isWritableSandbox(s: unknown): s is { commands: { run: (cmd: string, opts?: object) => Promise<{ exitCode: number; stdout?: unknown }> } } {
  return !!s && typeof s === 'object' &&
    typeof (s as any).commands?.run === 'function';
}

try {
  await writeFileToSandbox(sandbox, normalizedPath, fullPath, content);
} catch (err) {
  if (err instanceof Error && err.message === 'No available method to write files to sandbox') {
    console.error('Sandbox object lacks write capability; keys:', Object.keys(sandbox || {}));
    throw new Error('Sandbox provider not supported — create it via SandboxFactory.create("e2b" | "vercel")');
  }
  throw err;
}

When it happens

Trigger: Passing a custom, mock, or incorrectly constructed sandbox object lacking both a writeFile-style method and a commands.run method; instantiating a provider class that does not implement the expected interface; a refactor/version change that renamed the sandbox API surface.

Common situations: Unit tests injecting a partial sandbox stub; upgrading the sandbox SDK so method names changed (e.g. commands.run removed); wiring the wrong object (e.g. a config object) in place of the sandbox instance.

Related errors

• Unknown sandbox provider: ${selectedProvider}. Supported pro
• Unsupported sandbox type
• Failed to create zip: ${error}
• Failed to read zip file: ${error}
• Firecrawl API key not configured

AI-assisted analysis of firecrawl/open-lovable@69bd93bae7 (2026-08-28). Data as JSON: /api/errors/40e327e1fe49444e. Report an issue: GitHub.